The present invention relates to electromagnetic radiation monitors of the type which may be worn by persons who may be exposed to potentially harmful levels of electromagnetic energy. The invention has particular application to monitors for electric fields, specifically the 16w-frequency fields of the type which surround high-voltage conductors, such as power transmission and distribution lines.
Transmission lines route high-voltage (e.g., 2,000 volts and higher) electrical power from power plants to main regional stations and local substations. Distribution lines route high-voltage electrical power from substations to end users. Many such lines are above ground and exposed to the elements, requiring frequent inspection and/or repair or maintenance. Contact with such high-voltage power lines can be lethal for workers and, therefore, there have heretofore been provided various types of monitors or detectors to sense the proximity to dangerous high-voltage power lines to warn workers before they reach a dangerous proximity. One such type of detector senses the electrical field surrounding a high-voltage conductor, the strength and extent of such fields being proportional to the voltage level. Such detectors typically provide an audible and/or visible indication of the detected field to warn the user.
Prior detectors of the personal or wearable type are battery-powered and have on/off switches. One difficulty, particularly with detectors having audible alarm signals, is that when a worker has to work for an extended period of time in a sensed electric field, the continuous audible alarm can become annoying. Thus, workers will frequently turn off the detector, which can be dangerous. Also, a worker must remember to turn the device on each time he wears it, and failure to remember this is also dangerous.